errata.md

Errata

Changes made in the proofreading pass of October 2026 (Task 7 on the project board), that affect the published text (No Starch, 2023).

Only changes that affect the printed text are listed: one entry per change, by chapter and section, old text → new text. Content fixes are marked "(content)". Changes that appear only in the notebooks (solutions, hidden cells, layout, the examples, modsim.py) are listed in proofreading.md, along with the decisions behind the content fixes.

chap01

• False Precision: "a 1 meter railing" → "a 1-meter railing"
• Summary: "Empire State building" → "Empire State Building"
• Exercise 1: "side-by-side" → "side by side"
• Exercise 2: $sin^2 (\pi/4) + cos^2 (\pi/4)$ → $\sin^2 (\pi/4) + \cos^2 (\pi/4)$ (upright function names)
• Exercise 3: "a 10 foot pole" → "a 10-foot pole"
• Exercise 6: heading "Exercise 6:" → "Exercise 6"
• Exercise 6, step 1: "...with constant acceleration a." → "...with constant acceleration a?"
• The Falling Penny Myth (content): "The television show Mythbusters has tested the myth ... and a physical model of a human head." → "The science video channel Veritasium tested the myth of the falling penny more carefully, with help from Adam Savage of Mythbusters ... measurements of a penny falling at terminal velocity in a vertical wind tunnel, and research on how much force it takes to fracture a skull." (the link always went to the Veritasium video)

chap02

• Exercise 3, steps 4–5: "it should plot the results and / 5. Decorate the axes." → "it should plot the results. / 5. Then it should decorate the axes."
• Exercise 3, testing step 2: "Call run_simulation with parameters" → "with arguments" (the chapter defines the difference)
• Under the Hood: Matplotlib docs link from version 3.2.2 to the current docs (https://matplotlib.org/stable/api/axes_api.html)
• Modeling a Bike Share System (content): removed the repeated sentence "The State object is assigned to a new variable named bikeshare."

chap03

• Metrics: "system-owner's point of view" → "system owner's point of view"
• Summary: "We used a conditional operator, ==" → "We used a comparison operator, ==" (the chapter calls them comparison operators)
• Exercise 2: "run the simulation with parameters p1=0.3..." → "with arguments"

chap04

• Introduction: "bike sharing system" → "bike share system"
• Loops and Arrays: "equally-spaced" → "equally spaced"
• Sweeping Parameters and Under the Hood: Matplotlib colors links (one moved, one to version 3.3.2) → https://matplotlib.org/stable/users/explain/colors/colors.html
• Exercise 6 (content): "with a range of values for p1 and p2." → "with a range of values for p1 and these parameters:" (only p1 is swept)

chap05

• Introduction: "Paul Erlich" → "Paul Ehrlich"
• Absolute and Relative Errors: "counting everyone is the world is hard" → "counting everyone in the world is hard"
• Modeling Population Growth: "the second to last element" → "the second-to-last element"

chap06

• System Objects: "t0 and t_end are the first and last years" → "t_0 and t_end..."
• Under the Hood: "defined in the ModSim library, is based on" → "defined in the ModSim library is based on"; Python docs link from 3.7 to the current version
• Factoring Out the Update Function (content): "the second parameter is a function, like growth_func1, that computes the population for the next year" → "the second argument is a function, like growth_func1, that computes the net growth during the current year"

chap07

• Quadratic Growth: "the parameters alpha and beta ." → "the parameters alpha and beta."
• Net Growth: "To plot growth rate versus population" → "To plot net growth versus population"
• Introduction (content): removed "In the exercises, you will have a chance to try the second." (this chapter's exercises don't try a time-varying growth rate)
• Exercise 2 (content): "initial populations between 1 and 20 billion" → "between 1 and 25 billion" (matches the solution)

chap08

• Summary: "In this chapter we use the quadratic growth model" → "we used"
• Exercise 1: "time stamp" → "timestamp" (twice)

chap09

• Difference Equations (content): "The population models in the previous chapter and this one" → "The population models in the previous chapters"
• Analysis and Simulation: "see http://modsimpy.com/plato.)." → "see http://modsimpy.com/plato)."
• Solving the Quadratic Growth Model: added the missing period after the Khan Academy link
• Summary: $f(t) = p_0 \exp{\alpha t}$ → $f(t) = p_0 \exp(\alpha t)$ (the braces rendered without parentheses)

chap10

• Historical World Population: broken Wikipedia link (.../World_population_estimates.html, 404) → https://en.wikipedia.org/wiki/World_population_estimates

chap11

• The Kermack-McKendrick Model: "or the variables name beta" → "or the variable name beta"
• Heading "Implementing the KM model" → "Implementing the KM Model"
• Implementing the KM Model: "Now that we have object to represent" → "Now that we have objects to represent"
• Now With a TimeFrame: "a kind of a DataFrame" → "a kind of DataFrame"
• Running the Simulation (content): "The parameters of run_simulation are..." → "run_simulation1"; "initial conditions, and values of 0 and t_end" → "initial conditions, and t_end"; "We can call run_simulation like this" → "run_simulation1"
• Collecting the Results (content): "about five weeks (35 days) to peak" → "about four weeks (30 days) to peak" (the infected fraction peaks on day 30)

chap12

• Sweeping Immunization: "This following function" → "The following function"

chap13

• Sweeping Beta: "also called an f-string to assemble a label" → "also called an f-string, to assemble a label"

chap14

• Introduction: "Let's think what that relationship might be" → "Let's think about what that relationship might be"
• Contact Number: "we divided the contact rate by the infection rate to get $c$" → "by the recovery rate"
• Exploring the Results: -- → --- around the aside about metric
• Analysis and Simulation (content): the explanation of why simulation and analysis disagree when $c < 1$ was "the simulation divides time into a discrete series of days, whereas the analysis treats time as a continuous quantity." Now: the analysis assumes the initial number of infections is negligible (like a very large population); the simulation starts with one student, about 1% of the class, who infects a few others before recovering; when $c > 1$ these few are negligible compared to the outbreak. (A continuous-time model with the same start gives the same small totals, so discrete time is not the cause.)
• Estimating Contact Number (content): "anywhere from 20% to 80%, we would conclude that $c$ is near 2" → "anywhere from 25% to 60%, we would conclude that $c$ is near 1.3" (by the chapter's formula, 20%–80% is $c$ from 1.1 to 2.0; 25%–60% is 1.15 to 1.5, in the steep part of the curve)

chap15

• Temperature and Heat (content): "related to the average velocity of the particles" → "related to the average kinetic energy of the particles"
• Newton's Law of Cooling: "law " → "law"
• Implementing Newtonian Cooling: "time stamp" → "timestamp" (three places); the loc example said the world population labels start in 1960 → 1950
• Estimating r: "about -11°C" → "about -11 °C"

chap16

• Introduction: "root finding algorithm" → "root-finding algorithm"
• Mix First or Last?: "61.5 °C which is still" → "61.5 °C, which is still"
• Mix First or Last? (content): the mix-last case simulated the coffee for 30 minutes but the milk for only 15 (its t_end from the measurement). Now both run 30 minutes (milk.t_end = 30), and "the temperature is 62.9 °C" → "63.2 °C", which matches the end of the sweep. Re-executed
• Analytic Solution: "If we observe the that the temperature" → "If we observe that the temperature"; "the value of r we computed in the previous chapter, 0.115" → "0.0115"; "time stamps" → "timestamps"

chap17

• Introduction (content): dropped the dead "PDF at http://modsimpy.com/minmod" (the redirect went to an unrelated homepage; no free PDF found); /minmod now goes to the abstract, like /bergman
• The Minimal Model: "neither too high or too low" → "neither too high nor too low"; "Long term, severe hyperglycemia" → "Long-term, severe hyperglycemia"; "2--10 minutes" → "2–10 minutes"
• The Minimal Model (content): "affects almost 10% of the population in the U.S." → "about 12%" (CDC, 2023 data); /cdc now goes to the CDC's current report page
• The Glucose Minimal Model (content): "The initial state of the model is $X(0) = I_b$" → "$X(0) = 0$" (as in chapter 18's code and Bergman's model)
• Getting the Data (content): the Pacini and Bergman (1986) citation linked a different paper on ResearchGate → https://pubmed.ncbi.nlm.nih.gov/3640682/
• Interpolation: "equally-spaced" → "equally spaced"

chap18

• Introduction: "to solve the differential equation using a better algorithm" → "differential equations"
• "time stamp" → "timestamp" (three places)
• Running the Simulation (content): "X ... then declines as the concentration of glucose declines" → "as the concentration of insulin in the blood declines" (in the model, X is driven by I, not G)

chap19

• The Glucose Minimal Model: "least squares"; so-named because → "least squares", so named because
• The Insulin Minimal Model: "Berman et al." → "Bergman et al."
• HIV: the link to Phillips (1996) was dead (404) → https://doi.org/10.1126/science.271.5248.497 (the journal's page; the old link was a free copy); also removed a stray ")" and added "Science, 1996"

chap20

• Newton's Second Law of Motion: $H(x, y, \frac{dy}{dt})$ → $H(x, y, \frac{dy}{dx})$
• Dropping Pennies: "time stamp" → "timestamp"
• Exercise 1: "meters, kilograms, and Newtons" → "newtons"; the Ask an Astronomer link (dead, 404) → its Wayback Machine copy from 2018 (as greenteapress.com/matlab/astro already does)

chap21

• Drag Force (content): "Using the low end of their range, 40 mph" → "Using a value near the low end of their range, 40 mph" (the range is 35–65 mph)
• The Params Object: "inital state" → "initial state"; "the density of air, and acceleration due to gravity, and the observed terminal velocity" → "the density of air, acceleration due to gravity, and the observed terminal velocity"
• Simulating the Penny Drop: "time stamp" → "timestamp"

chap22

• Vectors: "the same angle and magnitude of A" → "as A"
• Simulating Baseball Flight: a colon after the Physics of Baseball link → period
• Drag Force: "in Newtons" → "in newtons"; "time stamp" → "timestamp" (twice)
• Visualizing Trajectories: "about 57° degrees" → "about 57°"
• Animating the Baseball: animate "takes ... a TimeSeries" → "a TimeFrame"

chap23

• Introduction: "the angle you should hit a baseball" → "the angle at which you should hit a baseball"; "called maximize_scalar that searches" → "called maximize_scalar, that searches"
• The Manny Ramirez Problem: "the angle the ball should leave home plate" → "the angle at which the ball should leave home plate"
• Finding the Range (content): "The first parameter is the function we want to maximize. The second is the range of values we want to search" → "The first argument is the function we want to maximize. The second is params, which maximize_scalar passes along to range_func. The keyword argument bounds is the range of values we want to search"
• Exercise 1: the error function "takes a speed and a System object" → "a Params object"
• Under the Hood: stray ")" after the link; /minimize (Golden-section search) now goes to Brent's method, which the text describes

chap24

• Simulating the System: "time stamp" → "timestamp"; "The final value of r is 0.55 m" → "0.055 m"
• Analytic Solution (content): the label "(1)" moved from $d\theta/dt = \omega$ to $dr/dt = k \omega$, so "Dividing Equations 1 and 2 yields $dr/dy = k/r$" is correct (dividing $d\theta/dt$ by $dy/dt$ gives $d\theta/dy = 1/r$)
• Analytic Solution (content): "the same as the "estimate" we computed in Section xxx" → "earlier in the chapter"

chap25

• Angular Acceleration: "newton meters (Nm)" → "newton meters (N m)"
• Teapots and Turntables (content): "its weight is 7 kg" → "its mass is 7 kg"; "The teapot weights 0.3 kg" → "The mass of the teapot is 0.3 kg"
• Heading "Two Phase Simulation" → "Two-Phase Simulation"
• Estimating Friction (content): "0.333 N m, a little less than the initial guess" → "a little more" (the guess was 0.3)

chap26

• Bungee Dunk Revisited: "In the previous case study, we assume" → "we assumed"; a stray "." before ")" in the Heck et al. citation
• Heading "Spider-man" → "Spider-Man"; "Spider-Man weighs 76 kg" → "has a mass of 76 kg" (as in chap25)
• Simulating a Yo-yo: "rolled up string" → "rolled-up string"; "counter-clockwise" → "counterclockwise" (twice); an empty last row (\\ before \end{aligned}) removed from the results

chap27

• Introduction: "Most of the time you don't need to know, you can use" → "you don't need to know; you can use"
• How root_scalar Works: missing period after the SciPy link; a stray backtick before "You just invented a numerical method called bisection"
• How maximize_scalar Works: alt text for the second golden-section figure (was empty)